A container comprises, conventionally, a body that delimits the general volume of the container, extended, at an upper end of the container, by a neck, through which the container is filled and emptied, and, at a lower end, by a bottom that closes the container.
The bottom must be able to bear, without significantly deforming, at least the hydrostatic pressure of the column of liquid that is above it. Many shapes of bottoms exist, depending on the applications concerned. Thus, for carbonated applications (typically sodas), the bottoms generally have a petaloid shape, comprising an alternation of valleys, of hemispherical shape, and projecting feet, whose ends form a base for the container (see, for example, the French patent application FR 2 959 214 or its U.S. equivalent US 2013/043255).
The petaloid-shaped bottom appears as a relatively successful solution exhibiting a good resistance to the strong internal pressures in the container (thanks to the hemispherical shape of the valleys).
However, the petaloid-shaped bottom requires a considerable amount of material (on the order of 15 to 18 g for a 0.5 liter container), as well as a relatively high blow molding pressure, to ensure a proper impression-taking of the feet and valleys. These constraints appear justified, however, by the relatively high price at which the products concerned are distributed.
The petaloid-shaped bottoms, however, may not be suitable for flat-liquid-type applications (typically table water), for which the blow molding pressure and the amount of material used (today on the order of 10 g for a 0.5 liter container) are minimized.
A bottom provided with a simple concave arch is not able to support without significant deformation the hydrostatic pressure alone of the liquid that is above it. Therefore, it has been proposed to provide the bottom with radial ribs, intended to reinforce the bottom to make it possible for it to better withstand the deformations caused by the pressure of the contents.
Now, it is becoming common for certain applications of flat liquids that are susceptible to oxidation (particularly fruit juices, but also certain plain waters) to remove the air above the flat liquid and to replace it with an inert gas (typically nitrogen). In practice, this operation is performed by adding a drop of liquefied inert gas to the surface of the flat liquid, immediately preceding the capping of the container. This operation, referred to as inerting (nitrogenating in the case of nitrogen), causes an excess pressure in the container. Although seemingly slight (on the order of 0.5 to 1 bar), this excess pressure is enough to considerably increase the stresses that are exerted on the bottom.
It has been proposed by the applicant to improve the ribbed bottoms by introducing a variability in the depth of the grooves, see, for example, French patent FR 2 753 435 (Sidel), to make it possible for the bottom to offer enough mechanical strength to bear the excess pressure due to nitrogenating. However, the savings demands of the market, or even certain anti-pollution standards, lead the manufacturers to use ever less material. Other things being equal, the result is a reduction in the mechanical performance of the bottom. This is particularly the case of the bottom described in the aforementioned patent, such that it consequently appears necessary to enhance it to maintain, indeed improve, its performance without, however, adversely affecting its blowability (i.e., its ability to be properly shaped by blow molding).